Calender and method for controlling such a calender

ABSTRACT

A calender includes a rotatable roller, and a belt co-acting with the roller with a determined belt pressure. At least one material for feeding through the calender is situated between the roller and the belt for a determined contact time during throughfeed through the calender. The calender also includes means for heating the fluid and/or the roller, control means for controlling the heating means and/or the belt pressure and/or the contact time, and at least one first temperature sensor for measuring the temperature of an outer periphery of the roller and at least one second temperature sensor for measuring the temperature of the fluid. The control means are configured to control the heating means and/or the belt pressure and/or the contact time on the basis of the measured outer periphery temperature and the measured fluid temperature. A set with a plurality of such calenders and a method for controlling such a calender.

The invention relates to a calender, comprising:

-   -   a rotatable roller, which roller is hollow and thereby defines        an internal space which can be filled at least partially or is        filled at least partially with a heatable fluid, such as oil or        air;    -   a belt, co-acting with the roller, with a determined belt        pressure, wherein a material for feeding through the calender is        situated between the roller and the belt for a determined        contact time during throughfeed through the calender;    -   heating means for heating the fluid and/or the roller, which        heating means are optionally disposed in the internal space; and    -   one or more control means for controlling the heating means        and/or the belt pressure and/or the contact time.

Such a calender is per se known. Particularly known are different typesof calender. There is thus for instance a type of calender which is usedfor throughfeed of a material, wherein a print is fixated on thematerial if the material already had a print printed thereon prior tothroughfeed through the calender, or is transferred thereto from aso-called transfer paper if the material did not yet have a print priorto throughfeed through the calender. Such a calender can also bereferred to as a device for transfer and/or fixation. Another type ofcalender is a laminating calender or laminating device, wherein multiplematerials are fed through the calender and are here bonded to eachother, i.e. laminated. The material or the materials can be any desiredand/or suitable material, such as for instance textile.

The calendering process takes place under the influence of heat. Theheat comes from the heating means which heat the fluid, such as oil orair, whereby the roller is heated by the heated fluid, and optionally inthat the heating means heat the roller directly, for instance byradiation. Direct heating of the roller by for instance radiation takesplace particularly in the case of air-filled rollers. Indirect heatingby the heating means via the heatable fluid takes place particularly inthe case of both oil-filled and air-filled rollers. The heating can beset as desired, particularly by controlling the heating means in desiredmanner Controlling the heating means can for instance comprise ofcontrolling a power of the heating means.

The calendering process further takes place under the influence ofpressure. The pressure is provided by said belt and can be set asdesired, particularly by controlling the belt pressure in suitablemanner, more particularly by tightening the belt or arranging the beltmore loosely, whereby the pressure is respectively increased andreduced.

In addition to the heat and pressure, the contact time, i.e. the amountof time that the at least one material is in direct or indirect contactwith the roller, can also be particularly important for the calenderingprocess. The contact time can be set as desired, for instance byselecting a rotation speed of the roller. Controlling of the contacttime can therefore alternatively or additionally be formulated ascontrolling of the roller, more particularly controlling of the rotationspeed of the roller, still more particularly controlling of drive meansfor rotating driving of the roller.

For the sake of simplicity the one or more control means are alsoreferred to below as “the control means”.

The control means control the heating means and/or the belt pressureand/or the contact time such that a desired calendering process shouldbe achieved. It has however been found by applicant that, despite thiscontrol, the result of the calendering process is not always fully asdesired and/or consistent. It is an object of the invention to at leastreduce or preferably obviate this drawback.

This object can be achieved by means of a calender according to claim 1.

It has been found by applicant that the temperature of the outerperiphery of the roller determines to a large extent the calenderingprocess. It is therefore opted for according to the invention to measurethe temperature of the roller at the position which substantiallydetermines the process, i.e. at the outer periphery of the roller.Provided for this purpose is at least one first temperature sensor, alsoreferred to below as the first temperature sensor, which measures thetemperature at the outer periphery of the roller, i.e. at the externalsurface of the roller, more specifically at a position where thematerial comes into contact with the roller and/or in or close to thecentre of the roller and/or in the area lying at a distance of at least20 centimetres from the edges of the roller. When only one firsttemperature sensor is provided, it is preferably arranged in or close tothe centre of the roller.

It has further been found by applicant that a determined, measured outerperiphery temperature of the roller can require determined settingsand/or adjustments in the control of the the heating means and/or thebelt pressure and/or the contact time which result in a good and/orconsistent calendering process. The one or more control means accordingto the invention are therefore configured to control the heating meansand/or the belt pressure and/or the contact time on the basis of themeasured outer periphery temperature. Controlling of the heating meansand/or the belt pressure and/or the contact time can for instancecomprise of setting and/or adjusting the heating means and/or the beltpressure and/or the contact time.

It is possible, by way of example, that data are collected according tothe invention, wherein a connection is made between the control of theheating means and/or the belt pressure and/or the contact time and themeasured outer periphery temperature of the roller, particularly forcalendering processes in which a good and/or consistent calenderingresult has been achieved, and that a calendering process is controlledon the basis of these data. By collecting sufficient data from aplurality of calendering processes with the same or different calendersand recording these data in a database it is possible to determine onthe basis of the data contained in the database how the control meansmust control the heating means, the belt pressure and the contact timeat a determined, measured outer periphery temperature in order toachieve a good and/or consistent calendering result. This control on thebasis of the database can take place before, during and/or afterthroughfeed of the material.

The control means are preferably embodied as an electronic device withat least one input and one output and a processor, such as amicroprocessor, which device controls the at least one output on thebasis of the information at the at least one input, for instance aprogrammable logic controller (PLC).

The heating means can be disposed outside the internal space of theroller, but can alternatively also be disposed in the internal space.Disposing or placing in the internal space makes the calender morecompact, and further makes it possible to heat the fluid in the vicinityof the peripheral wall of the roller, so that a temperature change ofthe fluid relative to heating means disposed outside the roller resultsrelatively quickly in a change of temperature of the peripheral wall ofthe roller. In an embodiment the heating means can be embodied aselectrical heating element.

The fluid can be any suitable fluid but is preferably oil or air. It ispreferably contained in a system which is closed at least to said fluidand comprises at least the internal space of the roller, and optionallyfor instance an expansion tank connected via at least one conduit to theinternal space. And oil, such as particularly thermal oil, for instancemineral thermal oil or synthetic thermal oil, has a heat transfercoefficient suitable for the invention and can moreover be heatable to arelatively high temperature without this greatly reducing the lifespan.Oil can alternatively or additionally have a large heat capacity. Airhas the great advantage that it keeps the calender relatively simple andis able to increase or reduce the temperature of the roller relativelyquickly.

The roller will typically be a cylindrical body. During operation thisbody will generally be rotated about its rotation axis, in practicalmanner its width axis, at a desired rotation speed by means of drivemeans, wherein the material is carried over the outer periphery.

Although calendering processes, such as transfer and/or fixationprocesses or laminating processes, can be performed in continuousoperation, a batch process will however occur in most cases, including astart-up phase at the start of the batch process and a shutdown phase atthe end of the batch process.

The device according to the invention comprises at least one secondtemperature sensor for measuring the temperature of the fluid, whereinthe control means are further configured to control the heating meansand/or the belt pressure and/or the contact time on the basis of themeasured fluid temperature.

In addition to the at least one first temperature sensor, the calenderis thus provided with at least one second temperature sensor (alsoreferred to below as the second temperature sensor) which measures thetemperature of the fluid. By controlling on the basis of both the outerperiphery temperature of the roller and the fluid temperature thecalendering process can be performed well and/or consistently and/oraccurately.

In an embodiment of the device according to the invention the calenderor a system of which the calender forms part comprises a database inwhich at least one of the following data is stored, optionallyperiodically:

-   -   the measured outer periphery temperature of the roller;    -   a or the measured fluid temperature;    -   the contact time;    -   the belt pressure;    -   a power of the heating means;    -   number of revolutions of the roller since the start of a        calendering process;    -   at least one property of the at least one material being fed        through the calender;    -   at least one property of a transfer paper optionally being fed        through the calender;    -   an ambient temperature;    -   an air humidity;    -   which calender is used;    -   a power of drive means of the calender;    -   at least one property of a belt of the calender,

and the control means are further configured to control the heatingmeans and/or the belt pressure and/or the contact time on the basis ofat least one of the data contained in the database.

As elucidated above, the settings of the heating means and/or the beltpressure and/or the contact time and the measured outer peripherytemperature of the roller can be recorded in a database, and thecalender can be controlled on the basis of the data contained in thedatabase. The process can become even more accurate when otherparameters are also recorded in the database, and wherein the calendercan also be controlled on the basis of these other parameters. It hasbeen found by applicant that said parameters can influence thecalendering process and that it can thereby be useful to record at leastthese stated parameters. It will be apparent that other data can also bestored in the system, if desired. If desired by a skilled person, thesedata can likewise be used by the control means for the purpose ofcontrolling the heating means.

The parameters are preferably recorded in the database frequently, forinstance every 10 seconds or, if desired, less or more often. In orderto keep the amount of data limited it is possible to only registerchanges.

When the control means are moreover configured here to control theheating means and/or the belt pressure and/or the contact time beforeand/or during throughfeed of the material, a feed forward is achieved,whereby it is possible during the process to anticipate the influence ofchanges in one of the parameters which are stored in the database.

It has already been elucidated above that the outer peripherytemperature, fluid temperature and the settings of the heating meansand/or the belt pressure and/or the contact time can be important.

It will be briefly elucidated below how the further parameters could beused.

Recording data about the number of revolutions of the roller since thestart of a calendering process makes it possible to determine the numberof revolutions starting from which a good result can be obtained, and/orwhen the heating means can be switched off at the end of a calenderingprocess. If desired, the device can comprise means for making it knownthat a calendering process can be started, for instance visually bymeans of lighting.

Properties of the material, for instance type of material and/or(specific) weight, usually expressed in gram/m², often determine a heatabsorption by the material and thereby how the control means mustcontrol the heating means and/or the belt pressure and/or the contacttime. Registering the power of the heating means in combination withregistering the at least one property of the material can provideinsight into this heat absorption, for instance by registering theamount of energy, i.e. power, required to keep the outer periphery ofthe roller at a determined temperature without throughfeed of adetermined material, relative to the amount of energy required duringthroughfeed of a determined material. This information can be used toselect a determined power for the heating means even before a determinedmaterial is actually fed through. The operator can enter which materialwill be fed through, for instance via an interface of the device. For aheavier material it is for instance possible to select a greater powerthan for a lighter material, since the heat absorption of a heaviermaterial is usually higher than for a lighter material. This can beparticularly advantageous when starting up a calendering process andwhen switching between different materials.

Properties of the transfer paper, for instance humidity and/or type ofmaterial and/or (specific) weight, usually expressed in gram/m², candetermine a heat absorption by the transfer paper. By optionally alsoregistering this, it is possible also to control on the basis hereof.

The ambient temperature can influence the energy loss of the roller. Theheating means and/or the belt pressure and/or the contact time cantherefore be controlled in desired manner on the basis of a measuredambient temperature, for instance by increasing a power of the heatingmeans when the ambient temperature is lower than a determined value, andvice versa. An ambient temperature sensor can be provided for thepurpose of measuring the ambient temperature.

The air humidity can likewise influence the energy consumption of theroller. An air humidity sensor can be provided for the purpose ofmeasuring the air humidity.

Which calender is used can likewise influence a desired setting. Thiscan comprise both the type of calender, and which calender is used fromamong calenders of the same type.

The power of drive means of the calender can likewise be of influence.

The belt of the calender can absorb heat. When the at least one propertyof the belt is known, it is for instance known how great the energyabsorption of the belt in question can be, whereby the heating means canbe controlled on the basis of these data in order to improve the processstill further. Type of material and/or age of the belt can for instancebe determining factors.

As elucidated above, it is possible to register the amount of energy,i.e. power, required to keep the outer periphery of the roller at adetermined temperature without throughfeed of a determined material andwith throughfeed of a determined material. This registered energyprovides insight into how much energy leaks away without throughfeed ofmaterial, for instance due to heat absorption of the belt and/or due toradiation and/or due to a cold environment, and with throughfeed ofmaterial, due to heat absorption by the material. A more accurateprocess can be obtained by registering this energy by means ofregistering the power of the heating means and recording said parametersand controlling the heating means and/or the belt pressure and/or thecontact time on the basis thereof.

In another embodiment of the device according to the invention thecontrol means are configured to determine on the basis of at leastperiodically measured outer periphery temperatures and periodicallymeasured fluid temperatures of a plurality of prior calenderingprocesses and on the basis of at least the at least one property of thesame material how the heating means and/or the belt pressure and/or thecontact time must be set in order to obtain a desired outer peripherytemperature in the current calendering process, and to control theheating means and/or the belt pressure and/or the contact time in thedetermined manner.

It has been found that the outer periphery temperatures and fluidtemperatures as well as the properties of the material are highlydetermining parameters for the quality of a calendering process. Forthis reason it is preferred that, in controlling of the calender, valuesof these quantities from prior processes are considered or even used asa guide for setting of a current process. These can be data of one ormore calenders.

It is possible here to use one measured outer periphery temperature andone measured fluid temperature from prior processes, although thereliability of the process is increased further when the control meansare set on the basis of a plurality of measurements within one processrather than at least one of these two temperatures and/or when themeasurements are repeated multiple times in order to provide anindication of the reproducibility of the measurement.

This control can for instance be performed as follows. It is thus forinstance possible that it was established in a prior process that adetermined outer periphery temperature and determined fluid temperatureand determined settings of the heating means and/or the belt pressureand/or the contact time produced a good result for a determinedmaterial. On the basis of these data it is possible to opt in future tocontrol the control means such that the process progresses in the sameway, in any case in respect of these parameters, since this increasesthe chances of a good print quality.

In another embodiment of the device according to the invention thedatabase and the control means are connected or at least connectable toeach other, optionally wirelessly, for instance via a computer network,such as for instance the Internet.

In practical manner there is a connection between the database and thecontrol means. This connection preferably takes place via a computernetwork. This has the advantage that the data as collected on the basisof a plurality of calenders according to the invention can be collectedin one database. Because this one database contains all data relating tothe operation of a plurality of calenders, even more data are available,which can result in a more reliable operation of the calender with aview to a good quality. Central processing of these data in one databasemoreover has the advantage that these data can be secured more easilyand thereby more cheaply. Wireless connections are preferred herebecause they are very flexible and have sufficient bandwidth for theamount of data to be transferred.

It is possible for a connection between the database and the device todrop out at least temporarily. It can be advantageous for the controlmeans to be configured to control the heating means and/or the beltpressure and/or the contact time on the basis of average values, moreparticularly on the basis of average values for a determined fed-throughmaterial, as soon as this happens.

The temperature sensor can be any suitable sensor.

In another embodiment of the device according to the invention the atleast one first temperature sensor comprises a thermocouple arrangedagainst the outer periphery of the roller.

By arranging a thermocouple against the outer periphery of the roller avery direct measurement of the outer periphery temperature is achieved,which increases the chances of a reliable operation of the calender inrespect of the quality of a calendering process. This thermocouple canbe arranged against the outer surface at any suitable position. Thethermocouple is preferably disposed against the outer surface at alocation such that it is disposed at a position where the fed-throughmaterial diverges from the roller, i.e. at a position where the materialis not in direct contact with the roller but is guided away. Thethermocouple hereby does not influence the calendering process.

In another embodiment of the device according to the invention the atleast one first temperature sensor comprises an infrared sensor arrangedat a distance from the roller.

It is possible by means of an infrared sensor to measure the outerperiphery temperature at a distance, without the need for substantialmodifications to the calender itself. This makes this embodiment of thecalender simpler in terms of construction. An advantage hereof is thatthe sensor cannot influence the process itself. This infrared sensor canalternatively or additionally be provided on a thermocouple. Theinfrared sensor can particularly be used with a roller with a tefloncoating.

In another preferred embodiment of the device according to the inventionthe device comprises a plurality of temperature sensors which aredisposed distributed over the width of the roller for the purpose ofmeasuring the temperature of an outer periphery of the rollerdistributed over the width of the roller.

When a plurality of first temperature sensors is thus provided, thereliability of the measurement is increased. It is possible here thatwhen the calender is controlled on the basis of these multipletemperature sensors, each of these sensors is considered independently,or that an optionally weighted average of these measurements is used asstarting point. In both cases it is possible for the database to storethe data of the plurality of first temperature sensors independently ofeach other. Defects in a temperature sensor can hereby for instance bedetected. Such defects can for instance be caused by dust, and occurparticularly in the described temperature sensors which are embodied asthermocouple. When temperature sensors embodied as thermocouple areused, there is therefore preferably at least one further temperaturesensor, such as a thermocouple or another type of temperature sensor. Ifa sensor is deemed defective, it is thus possible not to include themeasurements of this sensor in the control of the calender, at leastuntil it is replaced. In such a case it is for instance possible totemporarily control on the basis of historical data from the sensor inquestion, or it is possible to control only on the basis of the othersensors. The first temperature sensors can here be embodied wholly orpartially as in the above described embodiments, or can take a differentform.

This advantage is here described particularly with reference to theouter periphery temperature and therefore the first temperature sensor,however, the same effect is also to be expected in the case that use ismade of a plurality of second temperature sensors for the purpose ofmeasuring the fluid temperature distributed over the width of theroller.

It is noted that it is possible using the plurality of temperaturesensors to determine whether there are any differences in temperatureover the width of the roller, which can cause variations in the process.

In another embodiment of the device according to the invention, thedevice further comprises flow influencing means for initiating and/orinfluencing a flow of the fluid in the internal space, wherein the oroptionally provided further control means are configured to control theflow influencing means and thereby the flow of the fluid in the internalspace in freely settable manner.

In this embodiment flow influencing means are provided which make itpossible to initiate a flow of the fluid in the internal space or, tothe extent that there already is such a flow, influence it. Theprovision is also made that the or optional further control means areconfigured to control the flow influencing means and thereby the flow ofthe fluid in the internal space, wherein the control means areconfigured to control the flow influencing means in freely settablemanner. The control means can be the same control means as those whichcontrol the heating means, or further control means which areadditionally provided. For the sake of simplicity, reference will bemade below of “the control means” for controlling of the flowinfluencing means and/or heating means, which can thus be understood tomean both the same control means and different control means. It isnoted that, if desired, “the control means” could alternatively bereferred to as “the optional further control means”.

It has been found by applicant that there can be a relatively greatdifference between a temperature of the fluid and an (outer periphery)temperature of the roller. Such a temperature difference can forinstance lie between 10° C. and 30° C., depending on the type ofcalender used. It has further been found by applicant that a heattransfer between the fluid and the roller can be influenced byinfluencing the flow of the fluid in the internal space, whereby thetemperature difference between the fluid and the roller can beinfluenced. The heat transfer between the fluid and the roller can forinstance be increased, whereby the difference in temperature between thefluid and the roller can be reduced. The heat transfer between the fluidand the roller can for instance be reduced, whereby the difference intemperature between the fluid and the roller can be increased. It hasbeen found by applicant that by also aiming for a flow of the fluid inaddition to controlling the heating means and/or the belt pressureand/or the contact time, a good and/or accurate calendering process canbe provided.

It has further been found by applicant that, particularly in the case ofan oil-filled roller, influencing the flow of the fluid with the flowinfluencing means can take place more quickly than influencing atemperature of the fluid with the heating means. According to theinvention, an (outer periphery) temperature of the roller can thereforebe adjusted relatively quickly, at least in the case of oil-filledrollers, by adjusting the flow of the fluid. Because the (outerperiphery) temperature of the roller can be adjusted relatively quicklyaccording to the invention, variations in the print on the substrate canbe reduced or preferably even prevented.

It has further been found by applicant that, particularly in the case ofan air-filled roller, a more homogenous heating with air can take placeby using the flow influencing means.

It is noted that the degree of heat transfer from the fluid to theroller can for instance be determined by temperature differences in thefluid, such as gradients in the fluid. When the temperature differencesin the fluid are small, particularly in the case of a small temperaturegradient in the direction of the roller, a heat transfer from the fluidto the roller can be relatively great. When the temperature differencesin the fluid are great, particularly in the case of a large temperaturegradient in the direction of the roller, a heat transfer from the fluidto the roller can be relatively small. By adjusting the flow of thefluid temperature differences in the fluid, particularly a temperaturegradient in the direction of the roller, can be adjusted, particularlyincreased or reduced, and with this the heat transfer to the roller.

It is further noted that freely settable can at least be understood tomean that the setting of the flow influencing means is independent orseparate from the setting of another component, such as for instance theroller, more particularly the rotation of the roller. Freely settablecan alternatively or additionally be understood to mean that the flowinfluencing means can be set not just to two values, such as on or off,but to at least a plurality of values. The setting can take place instepped manner or continuously.

It is further noted that the flow influencing means are preferablyprovided in addition to and/or separately of the roller so that they arefreely settable at least relative to the roller.

As elucidate above, the control means can preferably be configured toset the flow influencing means on the basis of a desired heat transferbetween the fluid and the roller. This can be achieved in diverse ways,alone or in any random combination. These ways will be elucidated belowon the basis of different embodiments of the device according to theinvention.

In an embodiment of the device according to the invention the controlmeans are configured to control the flow influencing means such that aflow speed of the fluid can be set.

The speed of the flow can at least partially determine the heat transferbetween the fluid and the roller. Because the control means can in thisembodiment control the flow influencing means such that this speed canbe adjusted, the option exists of adjusting the heat transfer betweenthe fluid and the roller.

Setting can here be understood to mean at least that the flow speed ofthe fluid can be adjusted or varied.

The flow speed of the fluid can particularly be set between 0, i.e.stationary, and V_(max), wherein V_(max) can for instance lie between 3and 15 m/s. The higher the speed, the higher a heat transfer to theroller can be and/or the more homogenous the temperature of the fluidcan be.

In another embodiment of the device according to the invention thecontrol means are configured to control the flow influencing means suchthat a direction of the flow of the fluid is substantially opposite to arotation direction of the roller.

A flow of the fluid in a direction substantially opposite to therotation direction of the roller provides a relatively high heattransfer between the fluid and the roller, i.e. a relatively smalltemperature difference between the fluid and the (outer periphery ofthe) roller. By setting the direction of the flow as being opposite tothe rotation direction of the roller, the heat transfer between thefluid and the roller, among other things, can be set hereby. Theopposite direction can here particularly be a tangential direction.

It is noted that setting of the direction of the flow can be achieved indifferent ways. Several practical embodiments will be elucidated belowon the basis of exemplary embodiments of the device according to theinvention.

The flow speed of the fluid can here be higher than, lower than or equalto the rotation speed of the roller, wherein the absolute value of theflow speed must be considered. If a higher heat transfer between thefluid and the roller is desired and the flow influencing means are setto make the fluid flow in the opposite direction, a fluid speed which ishigher relative to the rotation speed of the roller can preferably beopted for here.

In another embodiment of the device according to the invention thecontrol means are configured to control the flow influencing means suchthat the flow regime of the fluid can vary between turbulent andlaminar.

A turbulent flow of the fluid can provide a higher heat transfer betweenthe fluid and the roller relative to a laminar flow. Depending on adesired degree of heat transfer between the fluid and the roller, theflow influencing means can be set such that the flow is turbulent orlaminar.

As known to the skilled person, the transition from turbulent to laminaris determined on the basis of the Reynolds number Re and the geometry ofthe internal space.

Varying is here understood to mean that the flow regime in the fluid canbe both turbulent and laminar, and generally does not mean that itswitches continuously between the two.

The flow influencing means can be embodied in diverse ways.

The flow influencing means for instance comprise a rotatable rotor witha number of blades which is optionally disposed in the roller.

A rotor rotates about its rotation axis and has a relatively simpleconstruction and/or is relatively inexpensive, and can influence or atleast initiate the flow in the fluid in simple manner. The rotor canthus be rotatably driven at a desired rotation speed so as to set a flowspeed of the fluid and/or the rotor can be rotatably driven in adirection opposite to the rotor so as to make a flow direction of thefluid opposite to the rotation direction of the roller.

The rotor is preferably disposed in the roller, more particularly in theinternal space in the roller, because influencing of the flow canthereby be performed well and/or relatively quickly. The placement ofthe flow influencing means in the internal space can moreover mean thatless fluid is necessary to completely fill the internal space, whereby amaximum power of the heating means can be lower and/or the heating meanswill be able to achieve a heating of the fluid to a determinedtemperature more quickly.

In another embodiment of the device according to the invention devicecomprises first drive means for rotatably driving the roller and seconddrive means for rotatably driving the rotor, and the control means areconfigured to control the first and second drive means separately ofeach other.

It is advantageous for first drive means for the roller to be provided,which are separate or disconnected from second drive means for therotor. This makes it possible to set each of the roller and the rotor toits own rotation speed (with a determined rotation direction),independent of the other of the roller and the rotor, which can bedeemed favourable subject to the process conditions in a calenderingprocess. The control of the first drive means runs via said one or morecontrol means or via optionally further provided control means.

It is particularly advantageous here for the control means to beconfigured to control the first and second drive means such that therotor rotates in a direction opposite to the roller and/or rotates at arelatively high speed when the outer periphery temperature of the rolleris lower than a desired temperature of the outer periphery of theroller.

In combination therewith or as an alternative thereto, it is preferredthat the control means are configured during the start-up phase and/orshutdown phase of a calendering process to control the first and seconddrive means such that the rotor is rotated in a direction opposite tothe roller. During both starting up and shutting down of a calenderingprocess, such as a transfer and/or fixation process, this has the resultthat the outer periphery of the roller is brought to temperaturerelatively quickly (start-up phase) or that the heating means can beswitched off or can be set to a lower power sooner (shutdown phase).

The rotor can preferably be driven by the second drive means between aminimum rotation speed equal to 0 revolutions/s and a maximum rotationspeed V_(rotor, max), which maximum rotation speed can depend, amongother factors, on the fluid and/or a diameter of the rotor, and whichamounts to for instance 2 revolutions/s, wherein V_(rotor, max) isopposite to the rotation direction of the roller.

In another embodiment of the device according to the invention the rotorcomprises a cylindrical body disposed in the internal space of theroller, wherein the fluid is situated between the rotor and the roller,at least during use of the calender, wherein the blades extend outwardfrom the cylindrical body, substantially in the direction of the roller.

Such a rotor can be suitable for appropriately influencing the flow ofthe fluid.

When the rotor is embodied in this way, the volume that is filled withfluid is reduced to an annular space between the cylindrical rotor andthe peripheral wall of the roller, whereby relatively little fluid isnecessary in comparison.

The body can here be completely solid but also hollow, wherein a hollowmass has the advantage that this reduces the mass of the rotor, wherebyit can be rotated more easily and whereby the total mass of the deviceis also smaller.

It has been found by applicant that the rotation speed of the roller andthe rotation speed of the rotor can be related. It can therefore beadvantageous for the flow influencing means to also be controlled on thebasis of a number of revolutions of the roller. The number ofrevolutions of the rotor can thus for instance also be reduced when anumber of revolutions of the roller is reduced, and vice versa.

In another embodiment of the device according to the invention the flowinfluencing means comprise at least one fluid conduit extending into theinternal space and having at least one opening for the purpose ofsupplying fluid from the at least one fluid conduit via the at least oneopening to the internal space of the roller, and comprising at least onefluid discharge for discharging fluid from the internal space.

By providing the fluid conduit fluid can be supplied to the internalspace and discharged again via the discharge. Giving the fluid conduitand/or the opening a suitable form and/or selecting a suitable pressureand/or speed of the fluid inflow enables the flow of the fluid to beinfluenced in desired manner.

It is thus for instance possible to set the inflow direction of thefluid into the internal space, and thereby set a flow direction of thefluid in the internal space, by suitable selection of the at least oneopening and/or by providing orienting means, such as flaps or the like,which co-act with the opening. The opening can thus be formed as atangential opening which supplies the fluid in a direction opposite tothe rotation direction of the roller, or orienting means such as a flapcan be provided which orient the flow of the fluid in a directionopposite to the rotation direction of the roller when flowing outthrough the opening. By selecting a speed and/or pressure at which thefluid is supplied, a speed of the fluid flow can be set.

The at least one fluid conduit and the at least one fluid discharge canbe connected to each other, optionally outside the roller, in order tofeed fluid discharged via the fluid discharge from the roller back tothe roller via the at least one fluid conduit.

At least one pump can be provided for the purpose of extracting fluidvia the fluid discharge and/or for the purpose of supplying fluid viathe at least one fluid conduit and the at least one opening to theinternal space of the roller.

The at least one fluid conduit preferably extends over the whole widthof the roller.

The at least one fluid conduit preferably comprises a plurality ofopenings which are preferably disposed distributed with equal mutualpitch distance over the width of the fluid conduit.

The at least one fluid discharge is preferably embodied as a fluiddischarge conduit extending into the internal space and having at leastone opening.

The at least one fluid discharge conduit preferably extends over thewhole width of the roller.

The at least one fluid discharge conduit preferably comprises aplurality of openings which are preferably disposed distributed withequal mutual pitch distance over the width of the fluid conduit.

The openings of the fluid conduit and the fluid discharge conduit can bedisposed at the same or different width positions.

Two fluid conduits and two fluid discharge conduits are preferablyprovided, with an angular distance of 180° between the two fluidconduits and between the two fluid discharge conduits, and with anangular distance of 90° between a fluid conduit and an adjacent fluiddischarge conduit.

The invention further relates to a set with a plurality of calendersaccording to any one of the foregoing claims, wherein the control meansof at least one of the calenders are configured to control the flowinfluencing means and/or the heating means and/or the belt pressureand/or the contact time of that one calender on the basis of optionallyperiodically registered data of calendering processes performed with thecalenders of the set.

It will generally be apparent to the skilled person that the advantagesand/or elucidations described on the basis of the device likewise applyto the set according to the invention.

It is advantageous here for optionally periodically registered data ofcalendering processes performed with a plurality of calenders of a setto be used in order to control the flow influencing means and/or theheating means and/or the belt pressure and/or the contact time of acalender of the set. When a large number of calenders is used to collectdata relating to the progression of the performed calendering processes,these data can serve as a basis for subsequent processes in order toincrease the chances of a good quality of the print. This is becausecalendering processes are readily predictable the more parameters areknown and/or are controlled. Periodically registering the data increasesthe amount of available data and enables a more accurate control.

The invention further relates to a method for controlling a calenderaccording to any one of the claims 1-8, which method comprises thefollowing steps, to be performed in any suitable order, of:

a) measuring the outer periphery temperature of the roller;

b) controlling the heating means and/or the belt pressure and/or thecontact time by means of the one or more control means on the basis ofthe outer periphery temperature measured in step a);

d) measuring the fluid temperature, wherein in step b) the control meansalso control the heating means and/or the belt pressure and/or thecontact time on the basis of the fluid temperature measured in step d).

It will generally be apparent to the skilled person that the advantagesand/or elucidations described on the basis of the device likewise applyto the method according to the invention.

Steps a) and b) are preferably performed regularly and preferablysubstantially continuously in order to thus keep adjusting the processcontinuously for the purpose of achieving a good calendering result.

As described, the fluid temperature can also be measured in addition tothe outer periphery temperature in order to thus control the outerperiphery temperature.

If desired, step d) can be performed regularly or substantiallycontinuously.

The method can further comprise the step of:

c) setting or determining a target temperature for the outer peripheryof the roller;

wherein in step b) the one or more control means control the heatingmeans and/or the belt pressure and/or the contact time for the purposeof heating the outer periphery of the roller and/or keeping the rollerat the target temperature up to at least roughly the desired targettemperature.

Step c) can be performed by an operator who sets the control means in adesired manner, for instance via an interface. Step c) is alternativelyor additionally performed by determining a desired setting by means offor instance the control means, for instance on the basis of datacontained in the optionally provided database.

If desired, step c) can be repeated more often, for instance because thetarget temperature can change during the process.

Steps a) and b) are preferably performed regularly and preferablysubstantially continuously so that the control means are regularly andpreferably substantially continuously controlled on the basis of themeasured temperature in order to thus approach the target temperature asclosely as possible and/or maintain it.

It is possible that during heating, heating takes place to roughly thedesired target temperature. This means that a determined variationbetween the measured outer periphery temperature and the targettemperature is disregarded or is permitted. This variation is preferablya maximum of 5° C., more preferably a maximum of 2° C., more preferablya maximum of 1° C.

When a calender according to at least claim 2 is controlled in anembodiment of the method, the control means can also control the heatingmeans and/or the belt pressure and/or the contact time in step b) on thebasis of at least one of the data stored in the database.

As already described above in relation to the calender according to theinvention, it is preferred in methods to have the control take place onthe basis of at least one of the data stored in the database asdescribed, since this makes the process more predictable and/oraccurate.

It must furthermore be noted that it is here also possible to provide amethod according to this embodiment, without this necessarily having thelimitations of the embodiments on which it is currently dependent,especially not the steps a), b) and c). In this alternative method theother embodiments can be considered for the same reasons.

In another embodiment of the method according to the invention, whereina calender according to at least claim 3 is controlled, the methodcomprises step e) of determining by means of the control means and onthe basis of at least periodically measured outer periphery temperaturesand periodically measured fluid temperatures of a plurality of priorcalendering processes and on the basis of at least the at least oneproperty of the same material how the heating means and/or the beltpressure and/or the contact time must be set in order to obtain adesired outer periphery temperature in the current calendering process,and of controlling the heating means and/or the belt pressure and/or thecontact time in the determined manner.

As already described above in relation to the calender according to theinvention, it is preferred in methods to have the control take place onthe basis of the outer periphery temperatures and fluid temperatures aswell as the properties of the material, because these are highlydetermining parameters for the quality of calendering processes asperformed with the calender according to the invention.

In another embodiment of the method according to the invention, whereina calender according to at least claim 8 is controlled, the methodfurther comprises the following steps, to be performed in any suitableorder, of:

f) setting or determining a setting of the flow influencing means;

g) controlling the flow influencing means, and thereby the flow of thefluid in the internal space, by means of the control means so as toachieve the setting set or determined in step f).

As already stated above, it is preferred to use the control means in thecalender according to the invention for the purpose of controlling boththe flow influencing means and the heating means and/or the beltpressure and/or the contact time, since this results in a better processcontrol.

Step f) can be performed by an operator who sets the control means in adesired manner, for instance via an interface. Step a) is preferablyperformed by determining a desired setting by means of for instance thecontrol means, for instance on the basis of a desired heat transferbetween the fluid and the roller, as elucidated above.

The method can comprise a step of controlling the flow influencing meanssuch that a flow speed of the fluid is set.

The method can comprise a step of controlling the flow influencing meanssuch that a flow direction of the fluid is set, wherein the direction issubstantially opposite to a rotation direction of the roller.

The method can comprise a step of controlling the flow influencing meanssuch that a flow regime of the fluid is varied between turbulent andlaminar.

During a start-up phase and/or shutdown phase of a calendering processthe flow influencing means can be controlled by the control means suchthat the direction of the flow of the fluid is opposite to the rotationdirection of the roller and/or the flow regime is turbulent.

In a preferred embodiment of the method according to the invention atleast steps a) and b) are performed iteratively.

Iteratively performing, i.e. repeating, the steps has the result thatthe process is monitored more closely, which increases the reliabilityof the control by the control means. This reduces thereby the chance ofvariations in a calendering process.

Since the method here also comprises the step d), this is likewisepreferably iteratively performed for the same reasons.

The invention further relates to a set with a plurality of calendersaccording to one or more of the above described embodiments or with oneor more of the above described features, wherein the control means of atleast one of the calenders are configured to control the flowinfluencing means and/or the heating means and/or the belt pressureand/or the contact time of that one calender on the basis of optionallyperiodically registered data of calendering processes performed with thecalenders of the set.

It will generally be apparent to the skilled person that the advantagesand/or elucidations described on the basis of the invention likewiseapply to the set according to the invention.

It is advantageous here for optionally periodically registered data ofcalendering processes performed with a plurality of calenders of a setto be used in order to control the flow influencing means and/or theheating means and/or the belt pressure and/or the contact time of acalender of the set. When a large number of calenders is used to collectdata relating to the progression of the performed calendering processes,these data can serve as a basis for subsequent processes in order toincrease the chances of a good quality of the print. This is because, asan increasing number of parameters are known and/or are controlled,calendering processes are readily predictable. Periodically registeringthe data increases the amount of available data and enables a moreaccurate control.

Said one calender is preferably a calender of the set other than thecalender of which the data are registered. In this way the progressionof the process in one or more other calenders can be used to efficientlycontrol this one calender.

The invention will be further elucidated with reference to theaccompanying figures, in which:

FIGS. 1A and 1B show schematically a calender according to a firstembodiment of the invention, wherein FIG. 1A shows a verticallongitudinal section along the width of the calender and FIG. 1B shows across-section of the calender;

FIGS. 2A and 2B show schematically a calender according to a secondembodiment of the invention, wherein FIG. 2A shows a verticallongitudinal section along the width of the calender and FIG. 2B shows across-section of the calender;

FIG. 3 show schematically the steps of a method according to a firstembodiment of the invention.

The same elements are designated in the figures with the same referencenumerals, increased by 100 for the second embodiment.

FIGS. 1A and 1B show a calender 1 according to a first embodiment of theinvention. Calender 1 can be used for calendering processes, such as forinstance transfer and/or fixation processes or laminating processes.Calender 1 comprises a rotatable roller 2, which roller is hollow andthereby defines an internal space 3 which in this case is filled withoil. Internal space 3 connects via a conduit 5 to an expansion tank 4for the oil. Calender 1 comprises a drive shaft 6 for rotating drivingof roller 2. Calender 1 further comprises a belt 7 co-acting with roller2, which belt 7 is disposed via guide rollers 8 round a part of theperiphery of roller 2, see FIG. 1B. For the sake of simplicity belt 7 isnot shown in FIG. 1A. As is visible in FIG. 1B, a material 9 can be fedthrough between roller 2 and belt 7 for a determined contact time duringa calendering process, wherein the contact time can particularly be theamount of time during which the material 9 is in direct or indirectcontact with roller 2. The contact time can for instance depend on arotation speed of roller 2. Disposed in this case in the internal space3 of roller 2 are a plurality of heating elements 10, which heat theoil. Because the oil is heated, the oil can heat roller 2. A calenderingprocess can particularly be controlled on the basis of at least one ofthe following three parameters, i.e. the degree of heating, which canfor instance be set by setting a power of heating elements 10, a beltpressure, which can for instance be set by tightening belt 7 orarranging it more loosely, for instance using guide rollers 8, and thecontact time, which can for instance be set by selecting a suitablerotation speed, i.e. number of revolutions, of roller 2. Calender 1comprises for this purpose one or more control means, for instance inthe form of a processor (not shown).

Several aspects of the invention will be elaborated further hereinbelow.The aspects can be provided alone or in combination. The elements ofcalender 1 further described in the context of the aspects can each beprovided alone or in combination.

According to an aspect of the invention, calender 1 comprises in thisfirst exemplary embodiment flow influencing means for initiating and/orinfluencing a flow of the oil in internal space 3. In this case the flowinfluencing means comprise a rotor 20 which is disposed in roller 2 andis rotatably drivable by a drive shaft 21. In this example rotor 20comprises a plurality of blades 22, using which the oil can be set intomotion. In this example rotor 20 comprises a cylindrical body, whereinthe blades 22 extend outward from the cylindrical body, substantially inthe direction of roller 2. The oil is situated between rotor 20 androller 2. The drive shaft 6 for rotating driving of roller 2 and thedrive shaft 21 for rotating driving of rotor 20 are configured to driveroller 2 and rotor 20 separately of each other. Rotor 20 canparticularly be driven in a rotation direction 23, which rotationdirection 23 is opposite to a rotation direction 24 of roller 2, seeFIG. 1B. The flow direction of the oil can hereby be set to a directionopposite to roller 2. The rotation speed of rotor 20 can be set between0 revolutions/s, i.e. the rotor does not rotate, and a maximum rotationspeed V_(rotor, max), for instance expressed in revolutions/s orrevolutions/min. A flow speed of the oil can hereby be set, particularlybetween a substantially stationary flow and a maximum flow speedV_(max). By selecting a suitable rotation speed for rotor 20 the flow ofthe oil can be laminar, i.e. for 0≤V_(rotor)≤V_(rotor, laminar), orturbulent, i.e. for V_(rotor, laminar)<V_(rotor)≤V_(rotor, max). Byselecting a suitable speed of the oil and/or the flow regime of the oila heat transfer from the oil to roller 2 can be set, and particularlyreduced or increased. The rotor can be controlled by the stated orfurther control means.

According to another aspect of the invention, in this first exemplaryembodiment calender 1 comprises at least one temperature sensor 30 formeasuring the temperature of an outer periphery of roller 2. Temperaturesensor 30 is disposed in an area of roller 2 where the material 9 willcome into contact with the roller, but at a position where material 9 isguided away from roller 2, see FIG. 1B. Temperature sensor 30 herebymeasures the outer periphery temperature at a location relevant to theprocess, but without influencing the calendering process. FIGS. 1A and1B show one first temperature sensor 30 but, if desired, a plurality offirst temperature sensors 30 can be provided, these being disposeddistributed over the width b of roller 2 for the purpose of measuringthe temperature of an outer periphery of roller 2 distributed over thewidth b of roller 2. First temperature sensor 30 is shown schematicallyin FIGS. 1A and 1B as being arranged on the outer periphery of roller 2.Such a sensor 30 can for instance comprise a thermocouple.Alternatively, it is also possible to dispose the sensor at a distancefrom roller 2, for instance by using an infrared sensor. In this firstembodiment of calender 1 the calender further comprises a secondtemperature sensor 31 for measuring the temperature of the oil. Ifdesired, a plurality of second temperature sensors 31 can be provided,these being disposed distributed over the width b roller 2 for thepurpose of measuring the oil temperature distributed over the width b ofroller 2. Such a sensor 31 can for instance comprise a thermocouple.Said control means can be configured to control the heating means and/orthe belt pressure and/or the contact time on the basis of the measuredouter periphery temperature and optionally the measured oil temperature.

According to another aspect of the invention, calender 1 or a system ofwhich the calender forms part comprises a database 40 which iswirelessly connected to calender 1 in this example. Data can be storedin database 40, wherein said control means can further be configured tocontrol the rotor 20 and/or the heating elements 10 and/or the beltpressure and/or the contact time on the basis of at least one of thedata contained in database 40. At least one of the following data canfor instance, though not exclusively, be stored, optionallyperiodically, in database 40:

-   -   the measured outer periphery temperature of roller 2;    -   the measured fluid temperature;    -   the contact time;    -   the belt pressure;    -   a power of heating elements 10;    -   number of revolutions of roller 2 since the start of a        calendering process;    -   at least one property of the at least one material 9 being fed        through calender 1;    -   at least one property of a transfer paper optionally being fed        through the calender;    -   an ambient temperature;    -   an air humidity;    -   which calender is used;    -   a power of drive means of the calender;    -   at least one property of the belt 7 of the calender.

If desired, database 40 can also store data of other calenders 1. Inthis way the calender can be controlled even more accurately.

FIGS. 2A and 2B show a calender 101 according to a second embodiment ofthe invention. Only the differences with the calender 1 according to thefirst embodiment of FIGS. 1A and 1B will be described here. For afurther description of calender 101 reference is made to the figuredescription associated with FIGS. 1A and 1B.

Calender 101 comprises a rotatable roller 102, which roller is hollowand thereby defines an internal space 103, which in this case is filledwith air. In this embodiment roller 102 forms a closed system for theair. Disposed in this case in the internal space 103 of roller 102 are aplurality of heating elements 110 which both heat the air and alsodirectly heat roller 102 by means of radiation.

In this second embodiment the flow influencing means for influencing theflow of, in this case, the air comprise two air conduits 125 with anumber of openings 128 via which air can flow into the internal space103 of roller 102. Openings 128 are formed and/or provided withorienting means such that the air flows into space 103 in a direction123 which is opposite to the rotation direction 124 of roller 102. Airconduits 125 extend through roller 102 and are connected via an outerside of roller 102 to, in this case, two air discharge conduits 126. Airdischarge conduits 126 comprise openings 129 for drawing in air. The airextracted via the air discharge conduits 126 can be supplied to roller102 again via air conduits 125. A pump 127 is provided for the purposeof extracting and blowing in the air. Pump 127 can be set between aminimum power of 0, wherein no extraction and blowing in of the airtakes place and wherein the air is substantially still, and a maximumpower V_(pump, max) whereby a maximum flow speed of the air is broughtabout. By selecting a suitable power for pump 127 the flow of the aircan be laminar, i.e. for 0≤V_(pump)≤V_(pump, laminar), or turbulent,i.e. for V_(pump, laminar)<V_(pump)≤V_(pump, max) By selecting asuitable speed of the air and/or the flow regime of the air a heattransfer from the air to roller 102 can be set, and particularly reducedor increased. The pump 127 can be controlled by the stated or furthercontrol means.

Said temperature sensors 130 and/or 131 can if desired also be providedin this second embodiment.

Said database 140 can if desired also be provided in this secondembodiment.

FIG. 3 shows the steps of a first embodiment of the method according tothe invention.

Step 50 comprises of setting or determining a setting of the flowinfluencing means. Step 51 comprises of measuring the outer peripherytemperature of the roller. Step 52 comprises of measuring the fluidtemperature. Step 53 comprises of setting or determining a targettemperature for the outer periphery of the roller. Step 54 comprises ofmaking data from a stated or other database available. Step 55 comprisesof controlling the flow influencing means and/or the heating meansand/or the belt pressure and/or the contact time for the purpose ofcontrolling a calendering process on the basis of at least one of thesettings of the flow influencing means set or determined in step 50,outer periphery temperature measured in step 51, fluid temperaturemeasured in step 52, target temperature set or determined in step 53,and data from the database made available in step 54.

Although the invention is elucidated above on the basis of a number ofspecific examples and embodiments, the invention is not limited thereto.The invention instead also covers the subject matter defined by thefollowing claims.

1. A calender, comprising: a rotatable roller, which roller is hollowand thereby defines an internal space which is configured to be filledat least partially with a heatable fluid; a belt, co-acting with theroller, with a determined belt pressure, wherein at least one materialfor feeding through the calender is situated between the roller and thebelt for a determined contact time during throughfeed through thecalender; heating means for heating the fluid and/or the roller, whichheating means are disposed in the internal space; one or more controlmeans for controlling the heating means and/or the belt pressure and/orthe contact time, at least one first temperature sensor for measuringthe temperature of an outer periphery of the roller, and at least onesecond temperature sensor for measuring the temperature of the fluid,wherein the one or more control means are configured to control theheating means and/or the belt pressure and/or the contact time on thebasis of the measured outer periphery temperature and the measured fluidtemperature.
 2. The calender according to claim 1, comprising a databasein which at least one of the following data is stored, periodically: themeasured outer periphery temperature of the roller; a or the measuredfluid temperature; the contact time; the belt pressure; a number ofrevolutions of the roller since the start of a calendering process; atleast one property of the at least one material being fed through thecalender; at least one property of a transfer paper optionally being fedthrough the calender; an ambient temperature; an air humidity; whichcalender is used; a power of drive means of the calender; and at leastone property of a belt of the calender, and wherein the control meansare further configured to control the heating means and/or the beltpressure and/or the contact time on the basis of at least one of thedata contained in the database.
 3. The calender according to claim 2,wherein the control means are configured to determine on the basis of atleast periodically measured outer periphery temperatures andperiodically measured fluid temperatures of a plurality of priorcalendering processes and on the basis of at least the at least oneproperty of the same material how the heating means and/or the beltpressure and/or the contact time must be set in order to obtain adesired outer periphery temperature in the current calendering process,and to control the heating means and/or the belt pressure and/or thecontact time in the determined manner.
 4. The calender according toclaim 2, wherein the database and the control means are connectable toeach other wirelessly or via a computer network.
 5. The calenderaccording to claim 1, wherein the at least one first temperature sensorcomprises a thermocouple arranged against the outer periphery of theroller.
 6. The calender according to claim 1, wherein the at least onefirst temperature sensor comprises an infrared sensor arranged at adistance from the roller.
 7. The calender according to claim 1,comprising a plurality of first temperature sensors which are disposeddistributedly over the width of the roller for measuring the temperatureof an outer periphery of the roller distributed over the width of theroller.
 8. The calender according to claim 1, further comprising flowinfluencing means for initiating and/or influencing a flow of the fluidin the internal space, wherein further control means are configured tocontrol the flow influencing means and thereby the flow of the fluid inthe internal space in freely settable manner.
 9. A method forcontrolling a calender according to claim 1, which method comprises thefollowing steps of: a) measuring the outer periphery temperature of theroller; b) controlling the heating means and/or the belt pressure and/orthe contact time by means of the one or more control means on the basisof the outer periphery temperature measured in step a); and c) measuringthe fluid temperature, wherein in step b) the control means also controlthe heating means and/or the belt pressure and/or the contact time onthe basis of the fluid temperature measured in step c).
 10. The methodaccording to claim 9, further comprising, before step b) the step of:setting or determining a target temperature for the outer periphery ofthe roller; wherein in step b) the one or more control means control theheating means and/or the belt pressure and/or the contact time for thepurpose of heating the outer periphery of the roller and/or keeping theroller at the target temperature up to at least roughly the desiredtarget temperature.
 11. The method according to claim 9, comprisingcontrolling a calender, the calender comprising: a rotatable roller,which roller is hollow and thereby defines an internal space which isconfigured to be filled at least partially with a heatable fluid; abelt, co-acting with the roller, with a determined belt pressure,wherein at least one material for feeding through the calender issituated between the roller and the belt for a determined contact timeduring throughfeed through the calender; heating means for heating thefluid and/or the roller, which heating means are disposed in theinternal space; one or more control means for controlling the heatingmeans and/or the belt pressure and/or the contact time, at least onefirst temperature sensor for measuring the temperature of an outerperiphery of the roller, and at least one second temperature sensor formeasuring the temperature of the fluid, wherein the one or more controlmeans are configured to control the heating means and/or the beltpressure and/or the contact time on the basis of the measured outerperiphery temperature and the measured fluid temperature; a database inwhich at least one of the following data is stored periodically: themeasured outer periphery temperature of the roller; a or the measuredfluid temperature; the contact time; the belt pressure; a power of theheating means; a number of revolutions of the roller since the start ofa calendering process; at least one property of the at least onematerial being fed through the calender; at least one property of atransfer paper optionally being fed through the calender; an ambienttemperature; an air humidity; which calender is used; a power of drivemeans of the calender; and at least one property of a belt of thecalender, and wherein the control means are further configured tocontrol the heating means and/or the belt pressure and/or the contacttime on the basis of at least one of the data contained in the databasewherein in step b) the control means is configured to control theheating means and/or the belt pressure and/or the contact time on thebasis of at least one of the data stored in the database.
 12. The methodaccording to claim 11, comprising controlling a calender, the calendercomprising a rotatable roller, which roller is hollow and therebydefines an internal space which is configured to be filled at leastpartially with a heatable fluid; a belt, co-acting with the roller, witha determined belt pressure, wherein at least one material for feedingthrough the calender is situated between the roller and the belt for adetermined contact time during throughfeed through the calender; heatingmeans for heating the fluid and/or the roller, which heating means aredisposed in the internal space; one or more control means forcontrolling the heating means and/or the belt pressure and/or thecontact time, at least one first temperature sensor for measuring thetemperature of an outer periphery of the roller, and at least one secondtemperature sensor for measuring the temperature of the fluid, whereinthe one or more control means are configured to control the heatingmeans and/or the belt pressure and/or the contact time on the basis ofthe measured outer periphery temperature and the measured fluidtemperature; a database in which at least one of the following data isstored periodically: the measured outer periphery temperature of theroller; a or the measured fluid temperature; the contact time; the beltpressure; a power of the heating means; a number of revolutions of theroller since the start of a calendering process; at least one propertyof the at least one material being fed through the calender; at leastone property of a transfer paper optionally being fed through thecalender; an ambient temperature; an air humidity; which calender isused; a power of drive means of the calender; and at least one propertyof a belt of the calender, wherein the control means are configured todetermine on the basis of at least periodically measured outer peripherytemperatures and periodically measured fluid temperatures of a pluralityof prior calendering processes and on the basis of at least the at leastone property of the same material how the heating means and/or the beltpressure and/or the contact time must be set in order to obtain adesired outer periphery temperature in the current calendering process,and to control the heating means and/or the belt pressure and/or thecontact time in the determined manner; which method further comprisingthe step e) of determining by means of the control means and on thebasis of at least periodically measured outer periphery temperatures andperiodically measured fluid temperatures of a plurality of priorcalendering processes and on the basis of at least the at least oneproperty of the same material how the heating means and/or the beltpressure and/or the contact time must be set in order to obtain adesired outer periphery temperature in the current calendering process,and of controlling the heating means and/or the belt pressure and/or thecontact time in the determined manner.
 13. The method according to claim9, comprising controlling a calender, the calender comprising: arotatable roller, which roller is hollow and thereby defines an internalspace which is configured to be filled at least partially with aheatable fluid; a belt, co-acting with the roller, with a determinedbelt pressure, wherein at least one material for feeding through thecalender is situated between the roller and the belt for a determinedcontact time during throughfeed through the calender; heating means forheating the fluid and/or the roller, which heating means are disposed inthe internal space; one or more control means for controlling theheating means and/or the belt pressure and/or the contact time, at leastone first temperature sensor for measuring the temperature of an outerperiphery of the roller, at least one second temperature sensor formeasuring the temperature of the fluid, wherein the one or more controlmeans are configured to control the heating means and/or the beltpressure and/or the contact time on the basis of the measured outerperiphery temperature and the measured fluid temperature; and flowinfluencing means for initiating and/or influencing a flow of the fluidin the internal space, wherein further control means are configured tocontrol the flow influencing means and thereby the flow of the fluid inthe internal space in freely settable manner; which method furthercomprises the following steps of: f) setting or determining a setting ofthe flow influencing means; g) controlling the flow influencing means,and thereby the flow of the fluid in the internal space, by means of thecontrol means so as to achieve the setting set or determined in step f).14. The method according to claim 10, wherein at least steps a) and b)are performed iteratively.
 15. A set with a plurality of calendersaccording to claim 1, wherein the control means of at least one of thecalenders are configured to control the heating means and/or the beltpressure and/or the contact time of that one calender on the basis ofperiodically registered data of calendering processes performed with thecalenders of the set.